Gavra- this is true, a child at some point has to make their own choices as long as those choices do not effect or obligate others. In this case, that choice will obligate the parents to support him and therefore it is not his choice to make on his own. As parents we must guide our children and show the paths their choices will lead. If a choice for learning only is made, then like others have said, the Parents must question the path of how they plan to be mepharnes their families on that choice?
In this era, where parents have large families and the economy does not allow for unlimited support for unlimited amounts of children and there are no organizations or institutions offering unlimited support this system has begun to collapse upon itself. There is nothing wrong with a parent fulfilling their obligation of teaching their son a parnasah. If that son chooses to sit and learn after having that knowledge under his belt, that is his choice. But if at some time he will have to face the decision that he will have to go out into the real world and make a parnasah he will have the knowledge and the means to do so.